1. Field of the Invention
The present invention relates to a work conveying apparatus and a work conveying method configured to convey a work by a carriage.
2. Description of Related Art
Conventionally, there is known a work conveying method in which a plurality of works assembled as a product are mounted on and conveyed by a plurality of continuously disposed carriages, respectively in order to mass-produce plural kinds of products.
Japanese Patent Laid-Open No. 2000-296422 discloses a work conveying method used for an assembly process in which plural kinds of works produced by different assembly processes are conveyed along a predetermined conveying path together, and a desired assembly operation is applied to each work in the middle of the conveyance.
In the work conveying method, the works are conveyed simultaneously by inputting a plurality of running carriages which is configured to mount the works thereon and arranged in contact with each other along the conveying path in sequence one by one to an upstream of the conveying path. Each of the running carriages has at an upper surface thereof a work mounting part and a forward and backward length of each carriage is adjustable. Before the running carriages are inputted to the upstream of the conveying path, a forward and backward length of each of the inputted running carriages is adjusted based on a kind of each work placed on the carriage.
Japanese patent Laid-Open No. 2005-144603 shows a work assembling line and a work conveying carriage in which a main pallet section for mounting a work thereon and configured to achieve an assembling operation and a presetting section to support a plurality of parts assembled to the work are disclosed. The work assembly line includes an assembly starting station to place the work on the main pallet section, a presetting station to place the parts on the presetting section and an assembly station to assemble the parts on the presetting section to the work on the main pallet section.
However, in the work conveying method disclosed in Japanese Patent Laid-Open No. 2000-296422, because grooves for forming an outward conveying path for the carriages must be provided in a floor of a factory and tunnels for forming a homeward conveying path for the carriages must be provided below the outward conveying path, it is difficult to change an assembly system.
Moreover, the work conveying method disclosed in Japanese patent Laid-Open No. 2005-144603, because the main pallet section to support the work can be moved on a pair of rails, a considerable time and a lot of trouble are required to move the rails. Accordingly, there is a problem that even if the change of the work producing processes is required, the change of layout of the conveying path or system is difficult, and the system and the repair are expensive.
In both the work conveying methods as mentioned above, if the plurality of running carriages or stations are connected and moved, it is necessary to a considerable power for a drive motor. In particular, if an assembly operation is executed at each assembly operational position, because the movement and stop of the work are intermittently conducted, there is a problem that a higher power is required for the drive motor, thereby a larger energy is expended.